1. Field of the Invention
The present invention relates to quartz with which to form a chamber, susceptor, or other jigs used for the manufacture of semiconductors, an apparatus for manufacturing the quartz, and a method for manufacturing the quartz.
2. Description of the Related Art
In general, fused quartz is utilized for the manufacture of jigs which have to be formed of quartz. The fused quartz is obtained by fusing quartz crystal powder by means of a burner or an electric furnace. Where the burner is employed, the quartz powder is fused by the oxyhydrogen flame in the atmosphere containing H.sub.2 and O.sub.2. Where the electric furnace is employed, the quartz crystal powder is fused in the vacuum atmosphere by the heat generated by the heater. However, the fused quartz obtained in these processes has the following drawbacks:
Although quartz is a material which cannot be easily softened, it may deform when heated at a temperature higher than 1,100.degree. C. Therefore, it is not desired to use quartz as the material of jigs which are subjected to high-temperature processing, such as high-temperature annealing.
In addition, quartz permits easy permeation of a metal which has a high diffusion coefficient in quartz, such as Cu or Ni. That is, quartz cannot be used for forming a chamber which is used for treating such metals.
Further, particles of boron (B) or aluminum (Al) may easily attach to quartz. If a chamber having such an impurity is used for a long time, the impurity may be emitted from the quartz constituting the chamber, resulting in contamination of semiconductor substrates.
If quartz is used for forming a chamber or a susceptor of a CVD apparatus which forms films by use of chemical vapor phase growth, the films attaching to the susceptor or the inner wall of the chamber have to be removed regularly. During the cleaning process for this removal, the chamber or susceptor formed of quartz may be damaged.
When a film to which a large amount of phosphorus (P) or B is added by use of vapor phase growth is formed on a wafer, the wafer has to be held by a jig. If this jig is formed of quartz, it is likely that the jigs will be damaged by the diffusion of P or B. The jig may crack when the temperature for treatment is greatly raised or lowered.